1. Field of the Invention
The present invention relates to a sewing machine used in hemming of J-shaped folded cloth.
2. Description of the Related Art
Usually, a sewing machine used in hemming of J-shaped folded cloth comprises, as shown in FIG. 4, a needle plate 102 having a portal shaped needle hole 100 and the feed dog slots 104, 105, 106, and the feed dogs (omitted in FIG. 4) projecting and retracting on the top of the needle plate 102 from the first to third feed dog slots 104, 105,106. The portal shaped needle hole 100 has two needle drop portions 100b through which two needles 100a (see FIG. 5) pass. The first feed dog slots 104,104 of the needle plate 102 are disposed at the right and left side across the portal shaped needle hole 100, each extending before and after the portal shaped needle hole 100 in a state parallel to the cloth feed direction F. The second feed dog slots 105,105 of the needle plate 102 are a pair disposed at the right and left side ahead of the portal shaped needle hole 100 in the cloth feed direction F. The third feed dog slots 106,106 are a pair disposed at right and left side behind the portal shaped needle hole 100 in the cloth feed direction F. The J-shaped folded cloth set on the needle plate 102 is fed in the cloth feed direction F by means of the feed dogs.
In the conventional sewing machine having the needle plate 102 and the feed dogs projecting and retracting from the feed dog slots 104, 105, 106, when the feed dogs descend, a cloth end Wb of the folded portion Wa of the J-shaped folded cloth W as shown in FIG. 5 drops into the left side second feed dog slot of the pair of right and left second feed dog slots 105,105 and the dropping state continues until just before the portal shaped needle hole 100. Accordingly, the cloth end Wb of the folded portion Wa is deviated in lateral position with respect to the needle plate 102. In this lateral position deviated state, if the folded portion Wa of the J-shaped folded cloth W is sewn near the cloth end Wb, as shown in FIG. 5, the spacing margin between the outlet seam end Wbb of the folded portion Waa sewn to the cloth main body WW and the seam S is not constant, and a corrugated state is formed, and the appearance of the sewn product is impaired. Besides, the cloth end Wb dropping into the left side second feed dog slot is sent by following up the side end 105a of the left side second feed dog slot, and, as a result, the spacing between the outlet seam end Wbb and the seam S is not as specified.